Processing expectations

In the UNIX world, this character is almost
universally the dash or hyphen although plus signs and double dashes
have become more common in recent years.

In the DOS/Windows world, forward slashes are somewhat more common than
dashes.

The DocBook processing expectations on this point are intentionally
vague. In some environments it may be most convenient to
generate these characters automatically, in other environments
it may be more convenient to insert them literally in the
content.

Whichever processing model you choose, note that this will be an
interchange issue if you share documents with other users (see
Appendix F).

Brackets are used to distinguish between optional, required, or
plain arguments. Usually square brackets are placed around
optional arguments, [-g], and curly brackets are placed around
required arguments, {-g}. Plain arguments are required, but are
not decorated with brackets.

Repeatable arguments are followed by an ellipsis.

Multiple arguments within a group are considered exclusive and are
separated by vertical bars.

Groups, like arguments, may be optional, required, or plain and may or
may not repeat. The same brackets and ellipses that are used to
indicate these characteristics on arguments are used on groups.

Arguments and groups may nest more-or-less arbitrarily.

Formatted as a displayed block. The processing system is free to introduce line breaks
where required, but the SBR element may be introduced
by the author to provide an explicit break location.